Lecture 9 - Microbial Genetics Flashcards
1
Q
4 different levels of genetic study
A
organism level
cell level
chromosome level
molecular level
2
Q
the sum of all types of genes constituting an organism’s distinctive genetic makeup
A
genotypes
3
Q
the expression of the genotype that creates certain structures or functions
A
phenotype
4
Q
where is DNA found in microorganisms?
A
cells
- eukaryote
- prokaryote
- viruses
5
Q
basic unit of DNA is
A
nucleotide
6
Q
each nucleotide is composed of: (3)
A
- phosphate
- deoxyribose sugar
- nitrogenous base
7
Q
two types of nitrogenous bases
A
purines and pyrimidines
8
Q
adenine pairs with
A
thymine
9
Q
guanine pairs with
A
cytosine
10
Q
original parental DNA strand
A
template strand
11
Q
DNA goes under what type of replication
A
semiconservative replication
12
Q
where is the origin of replication for DNA?
A
short sequence rich in adenine and thymine bases that are held together by only two hydrogen bonds. (TATA box)
13
Q
because the origin of replication is AT-rich, ——– energy is required to separate the two strands than would be required if the origin were rich in G and C.
A
less energy
14
Q
unwind the DNA helix
A
topoisomerase
15
Q
unzips the DNA heliz
A
helicases
16
Q
DNA replication - figure 9.6
A
17
Q
synthesizing an RNA primer
A
primase
18
Q
adding bases to the new DNA chain; proofreading the chain for mistakes
A
DNA polymerases III
19
Q
removing primer, closing gaps, repairing mismatches
A
DNA polymerase I
20
Q
final binding of nicks in DNA during synthesis and repair
A
ligase
21
Q
making single-stranded DNA breaks to relieve supercoiling at origin
A
topoisomerase I
22
Q
making double stranded DNA breaks to remove supercoiling ahead of origin and separate replicated daughter DNA molecules
A
topoisomerase II and IV
23
Q
figure 9.7
A
24
Q
DNA is used to synthesize RNA
A
transcription
25
RNA used to produce proteins
translation
26
transcription figure 9.12
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27
translation figure 9.15
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28
Drugs that inhibit protein synthesis:
rifamycins
| actionomycin D
29
Drugs that interfere with the ribosome:
Erythromycin
Spectinomycin
Chloramphenicol
Aminoglycosides
30
- Found only in bacteria and archaea
- Coordinated set of genes regulated as a single unit
- Can be inducible or repressible
- Categories determined by how transcription is affected by the environment surrounding the cell
operons
31
- Catabolic operons; operons encoding enzymes that act in catabolism
- Operon is turned on (induced) by the substrate(s) for which the structural genes encode
- Enzymes needed to metabolize a nutrient are only present when that nutrient is present in the environment
inducible operons
32
- Contain genes coding for anabolic enzymes
| - Several genes in a series are turned off (repressed) by the product synthesized by the enzyme
repressible operons
33
3 features of the lac operon
- regulator
- control locus
- structural locus
34
composed of the gene that codes for the repressor, a protein capable of repressing the operon
regulator
35
two parts of the control locus
promoter and operator
36
recognized by RNA polymerase
promoter
37
acts as an on/off switch for transcription
operator
38
made up of three genes, each coding for a different enzyme needed to catabolize lactose
structural locus
39
figure 19.8
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40
Lac Operon Regulates Genes Based on Lactose Availability
----???
41
usually in the on mode
repressible operons
42
Will only be turned off when the nutrient is no longer required
repressible operons
43
serves as a corepressor to block the action of the operon
excess nutrient
44
figure 9.19
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45
what type of cells do not have operons
eukaryotic cells
46
together these interact with the promoter
enhancer and mediator
47
- Regulate gene expression for thousands of bp away
- Position independent
- DNA between enhancer and promoter loops out so that enhancer proteins can interact with proteins bound to the promoter
enhancer
48
- Large complex of proteins that mediate interaction between enhancer binding proteins and general transcription factors at the promoter
mediator
49
An event in which one bacterium donates DNA to another bacterium
recombination
50
what is the end result of recombination
a strain different from both the donor and recipient strain
51
extrachromosomal DNA adept at moving between cells
plasmids
52
any organism that contains and expresses genes that originated in another organism
recombinant
53
Any transfer of DNA that results in organisms acquiring new genes that did not come directly from parent organisms
horizontal gene transfer
54
three types of horizontal gene transfer in bacteria
conjugation
transformation
transduction
55
- A mode of genetic exchange in which a plasmid or other genetic material is transferred from a donor to a recipient cell via a direct connection
- Can occur in both gram-positive and gram-negative cells
conjugation
56
figure 9.20
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57
- Bear genes for resisting antibiotics or other drugs
- Commonly shared among bacteria through conjugation
- Can confer multiple resistance to antibiotics
- R factors can also carry genetic codes for resistance to heavy metals, or synthesizing virulence factors
resistance plasmids or factors
58
The acceptance by a bacterial cell of small fragments of soluble DNA from the surrounding environment
transformation
59
cells that are capable of accepting genetic material through transformation
competent
60
figure 9.22
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61
- The process by which bacteriophage serve as a carrier of DNA from a donor cell to a recipient cell
- Occurs in a broad spectrum of bacteria
- The participating bacteria in a single transduction event must be the same species
transduction
62
- Random fragments of disintegrating host DNA are taken up by a phage during assembly
- Any gene from the bacterium can be transmitted
generalized transduction
63
figure 9.23
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64
Transposable Elements - shifting segments of the genome
TE exists as a small DNA piece in genome
TE can change location (jump)
TE can replicate itself
The TE could insert into a plasmid and be transferred to other bacteria
65
The smallest TEs consist only of two tandem repeats
insertion elements
66
A type of TE that can transcribe DNA into RNA and then back into DNA for insertion in a new location
retrotransposon
67
Other TEs contain genes that code for
antibiotic or toxin production
68
Effects of TEs in bacteria:
- Changes in colony morphology, pigmentation, and antigenic characteristics
- Replacement of damaged DNA
- Intermicrobial transfer of drug resistance
69
The E. coli tet operon was originally identified as a _____ that confers resistance to the antibiotic tetracycline.
transposon (Tn10)
70
bind to the operator of the tetracycline-resistance operon – similar to how the lac operon works
TetR protein
71
- Have the ability to make their hosts pathogenic.
- Contain multiple genes that are coordinated to create a new trait on the bacterium
- Islands flanked by sequences that look like genes for TE enzymes
pathogenicity islands
72
Any change to the nucleotide sequence in the genome
| The driving force of evolution
mutation
73
A microorganism that exhibits a natural, nonmutated characteristic
The trait present in the highest numbers in a population
wild type
74
an organism that bears a mutation
mutant strain
75
A random change in the DNA arising from errors in replication that occur randomly
spontaneous mutation
76
result from exposure to known mutagens
induced mutations
77
Small mutations that affect only a single base on a gene
| Involve addition, deletion, or substitution of single bases
point mutations
78
mutations that lead to cell dysfunction or death
lethal mutation
79
produce neither adverse honor helpful changes
neutral mutation
80
Any change in the code that leads to placement of a different amino acids
missense mutation
81
Changes a normal codon into a stop codon that does not code for amino acid
nonsense mutation
82
Alters a base, but does not change the amino acid and has no effect
The redundancy of the code assures that certain amino acids will not be altered by a change in the third base of the codon
silent mutation
83
occurs when a gee that has undergone a mutation reverses to its original
back mutation
84
Occurs when one or more bases are inserted into or deleted from a newly synthesized DNA strand
frameshift mutation
85
This alters the reading frame of the mRNA
Nearly always result in a nonfunctional protein
Every amino acid after the mutation is different from what is coded for in the original DNA
Insertion of bases in multiples of three does not disturb the reading frame
frameshift mutation
86
Repair of damage caused by ultraviolet radiation
photoreactivation
87
Mutations are excised by a series of enzymes that remove the incorrect bases and add the correct ones
excision repair
88
Repair of damage caused by ultraviolet radiation
photoreactivation
89
Mutations are excised by a series of enzymes that remove the incorrect bases and add the correct ones
excision repair
90
- A repair system can locate mismatched bases that were missed during proofreading
- The base must be replaced soon after the mismatch is made, or it will not be recognized by the repair enzymes
mismatch repair
91
Commonly used to rapidly detect chemicals with carcinogenic potential
ames test
92
not repaired, permanent and heritable
mutations
